1. Field of the Invention
This invention relates generally to solar collector systems, and particularly to a device for synchronously rotating solar collectors of such a system.
2. Description of the Prior Art
It is known to mount a plurality of solar collectors in parallel rows with one or more collectors to a row. For concentrating collectors which focus the rays of the sun upon a small heat collecting surface, it is necessary to rotate the collectors in synchronization with the sun in order to cause the rays of the sun to intersect the heat collecting surface for the duration of the collecting period. For large rotation angles, such as plus or minus 90.degree. to plus or minus 180.degree., pulleys connected together by a continuous cable are generally used on each collector. The cable is looped around each pulley and fastened to the pulley at a single point. As the cable is pulled from one end to the other, the series of parallel collectors ccan be caused to turn in unison.
This scheme is satisfactory as long as the number of collectors to be turned is small and the torque required to turn the collectors is also small. If the required torque and/or the number of collectors is large, it becomes increasingly difficult to select a cable which is flexible enough to go around the pulleys and at the same time is large enough in cross section to prevent measurable elongation of the cable. As a consequence, it is difficult to keep all of the collectors turning in synchronization. That is, the collector at the end of the cable where the force is applied to the cable turns as the cable is pulled; however, the collector at the opposite end of the cable either does not turn immediately or does not turn as much as the first collector due to cable stretch.
A solution to this problem would be to use large diameter cable and large diameter pulleys. The large pulleys are necessary to reduce the force on the cable for a given required turning torque of the collectors and also to accommodate the thick cable. As a consequence, the expense of the arrangement increases rapidly as cable diameter and pulley diameter are increased.
U.S. Pat. No. 1,162,505, issued Nov. 30, 1915 to T. F. Nichols, discloses a solar boiler wherein a plurality of reflectors are simultaneously pivoted or rotated about associated conduits by means of a cable and pulley arrangement. Further, devices for collecting solar energy in which the collectors follow the sun and are driven by a motor and drive connection can be found in U.S. Pat. Nos. 509,393, issued Nov. 28, 1893; 820,127, issued May 8, 1906; 2,141,330, issued Dec. 27, 1938; 2,156,352, issued May 2, 1939; and 3,872,854, issued Mar. 25, 1975.